This application claims priority to an application entitled xe2x80x9cOptical System in Projection Television Receiverxe2x80x9d filed in the Korean Industrial Property Office on Jul. 24, 1999 and assigned Serial No. 99-30247, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates generally to an optical system in a projection television receiver and, more particularly, to an optical system in a projection television receiver in which R, G and B cathode ray tubes are arranged in a delta type array with a view to facilitating control of convergence.
2. Description of the Related Art
Unlike general televisions, the projection television receiver has three cathode ray tubes (CRTs) for red (R), green (G) and blue (B) colors and enlarges an image formed on the R, G and B CRTs through an optical system comprised of a plurality of reflecting mirrors and lenses, thereby displaying the enlarged image on a large-sized screen.
FIGS. 1 and 2 are diagrams illustrating the operational principle of an optical system in the related art projection television receiver and an array of R, G and B CRTs. Images each projected from R, G and B CRTs 100, 102 and 104 are enlarged at lens parts 106, 108 and 110, reflected by a reflecting mirror 112 and displayed on a screen 114. In the related art projection television receiver, as shown in FIG. 2, the R, G and B CRTs 100, 102 and 104 are arranged in a straight line with respect to the screen 114, i.e., the G CRT 102 is at the center of the screen 114, with the R and B CRTs 100 and 104 being positioned on the left and right sides, respectively, thereof. As the image projected on the screen 114 from the R or B CRT 100 or 104 has an excessively large angle of projection with respect to the image from the G CRT 102, as shown in FIG. 3, the images are out of accord with one another on the screen and thus the images are distorted. Such distortion of the image intensifies at the edges of the screen 114.
FIG. 4 shows distorted R, G and B images displayed on the screen due to straight arrangement of the CRTs. It is shown in FIG. 4 that distortion of the R, G and B images 400, 402 and 404 appear more significant on the left and right sides of the screen 114.
The related art projection television receiver, to overcome such a distortion problem, controls the convergence to make the images projected from the respective CRTs converged on a screen. However, compensation for the distortion of an image on the screen that results from the convergence control has a limitation and an excessive convergence control may incur an overload due to saturation of a power level.
It is, therefore, an object of the present invention to provide an optical system in a projection television receiver for facilitating control of convergence.
To achieve the above object, there is provided an optical system in a projection television receiver including: a screen for simultaneously displaying R (Red), G (Green) and B (Blue) images thereon; and a light source part comprising R, G and B cathode ray tubes. The R and B cathode ray tubes project the R and B images on the screen via a reflecting mirror, with the G cathode ray tube being set together with the R and B cathode ray tubes in a delta type array and projecting the G image directly on the screen.